Plate tectonics is a scientific theory, which explains the structure and motion of the Earth’s outermost layer, the lithosphere, and other associated phenomena.
This theory was formulated in the 1960s, when new information about the Earth's magnetism, worldwide distribution of animal and plant fossils, phenomena of volcanoes and earthquakes, and the nature of the ocean floor was obtained.
The theory states that the lithosphere is broken up into seven large tectonic plates: the Pacific, Antarctic, Australian, Eurasian, South American, North American, and African plates. Several minor plates, such as the Philippines, Nazca, and Arabian plates, also exist.
The point at which these plates meet is known as a plate boundary. The plate boundary is classified into three different types: convergent, divergent, and transform, based on the relative motion of these plates.
Convergent boundaries occur when two lithospheric plates slide together to form a continental or subduction zone.
Divergent boundaries occur when two plates slide apart from each other.
Transform boundaries are formed when two plates slide past each other along transform faults.
Formation of an oceanic trench, mountain-building, volcanic activity, and earthquakes occur along the tectonic plate boundaries. The periodical lateral movement of the plates may vary from 0 to 100mm.
According to geologists, the higher strength of the Earth's lithosphere, when compared to the underlying asthenosphere, is responsible for the movement of tectonic plates. Variations in the lateral density of the Earth’s mantle cause convection.
Plate movement is said to be triggered by the motion of the ocean floor, which results in changes in gravitational forces and downward suction at the subduction zones. Another theory states that the motion of tectonic plates is due to the difference in forces generated by the movement of the Earth, and the tidal forces of the moon and the sun.
Sources and Further Reading